Dry cleaning



Aug. 20, 1963 P. v. WARREN ETAL DRY CLEANING Filed 001;. 7, '1953 45 Hlll' water is not properly distributed through the organic solvent.Hence, it will be understood that when we speak herein of emulsionscontaining oil-soluble dispersing agents or detergents and ater, it willbe understood that we mean such emulsions wherein the water is so finelydispersed asto form a substantially clear homogeneous emulsion in thewater-immiscible organic solvent, as viewed by the naked eye. It'is alsoimportant, for the most effective practice of our invention, that theentire system to be charged with water so that the emulsified waterpasses through the filter.

Our invention is also based, in part, on a procedure, and simple andetfectiveequipment for use therein, involving determining the electricalconductivity of the aforesaid dry" cleaning emulsions at periodic ornonperiodic intervals and" if, during use of such emulsions in thecleaning of a batch or successive batches of soiled fabrics, theelectrical conductivity'iias dropped to aputilizing Stoddard solvent asthe dry cleaning organic solvent, dioctyl sodiurnsulfosuccinate as thedispersing agent or detergent, and distilled water as the source ofwater,

i it is possible to plot curves showing the relationship of preciablybelow 1(l 10 'lmhos an amount of water and/or oil-soluble dispersingagent or dry cleaning detergent is addedto the emulsion so as to bringthe elect'rical conductivity thereof to not less than the aforesaidminimum value thereof.

Our invention is particularly advantageously practiced with theutilization, as the oil-soluble dispersing agent, of sulfate andsulfonate detergents containing an alkyl group of at least '8 carbonatoms and'usually between 8 and 18 carbon atoms, in the form of saltsthereof as, for in- 'stance, the alkali metal, ammonium and amine salts.In

addition to the examples thereof described above, salts of higher alkylaryl sulfonates such'as dodecyl benzene sul- 'fonate, octyl benzenesulfonate, nonyl naphthalene sulfonate, keryl benzene sulfonates, andthe like can be utilized. It is also particularly advantageous, in theespecially preferred embodiments of our invention, to utilizeproportions of oil-soluble dispersing agent or detergent,

on the non-volatile basis, of not less than about 1.5

based on the volume of the organic solvent, "and desirably within therange of about 1.5% to about 3%, a good average being about 2%. In thisconnection, it will be understood that dry cleaning detergents arecommonly marketed in the form of liquid or paste products and frequentlycontain diluents, volatile ingredients and'the like over and above thenon-volatile dry cleaning detergents proper. When wespeak of, forexample, 1.5% to 3% of the dry cleaning detergent, said percentages areon the non-volatile :active detergent basis.

The amount of Water added to the water-immiscible dry cleaning solventshould, in the particularly preferred embodiments of our invention, notbe appreciably less than 0.2%, by volume, and most-desirably ranges fromabout 0.2% to about 0.4% it being relatively uncommon that this latterfigure will be exceeded. So far as actual dry cleaning practice goes,these amounts of water are abnormally large but their use, under theconditions of the present invention, has been found to be mostadvantageous, cleaning of the fabrics being enhanced and "subsequentspotting operations being reduced to a substantial The optimumconditions under which the dry cleaning operation should be conducted,taking into account the over-all aspects, therefore, will, in general,involve the utilization of la water-immiscible dry cleaning organicsolvent emulsion containing from about 1.5% to about 3%, with a goodaverage of about 2%, of "an oil-soluble sulfate or sulfonate detergentcontaining an alkyl group of at least 8 carbon atoms, and from about0.2% toabout 0.4%, with a good average of about 0.3%, of water, the

electrical conductivity of said emulsion being not less In the light ofthe foregoing description, it Will be and "detergent content of suchemulsions, the greater the theirrefiecting the condition of the emulsionwith respect to the content of water and detergent therein. In the usualcase, the electrical conductivity readings of an emulsion containing arelatively high proportion of soluble impurities resulting from longcontinued use of the emul sion prior to distillation thereof will show asomewhat lower conductivity than a similar pure organic solvent solutioncontaining only the same amounts of oil-soluble detergent and Water.Suitable extrapolations can be resorted to, if desired, in situations ofthis kind, if deemed advisable, to take into account the effect ofsoluble impurities on the electrical conductivity of repeatedly used drycleaning emulsions. v

I While satisfactory results are obtained with electrical conductivitiesmaintained at not less than about 10 x10 mlios, we prefer to operate athigher levels as, for example, from about 40 to about l20 l0' mhos oreven higher, a particularly preferred range being from about 50 to aboutx10 rn-hos.

In the preferred manner of carrying out the present invention, intheso-called two bath system, for example, invdry cleaning systems whichinclude a washer-filtertrap assembly reserved for the detergentemulsions and a separate rinse and filter system, and wherein saidemulsion is continuously circulated through said washer-filter-trapassembly, the water-immiscible liquid organic solvent is activated withthe requisite amount of oil-soluble nonvolatile dry cleaning dispersingagent or detergent and the resulting solution is circulated through saidassembly to effect uniform distribution of said dispersing agent ordetergent throughout the entire body of organic solvent in the assembly.The requisite amount of Water is then added and the resulting mixture iscirculated through said assembly whereby to solubilize or emulsify thewater throughout the system, so that the solubilized or emulsified wateremulsion passes through the filter, and forms a substantially clearhomogeneous composition having an electrical conductivity not less thanabout 10X 10* mhos'. The soiled fabrics to be dry cleaned are thensubjected to the resulting dry cleaning emulsion in the usual way,successive batches of soiled fabrics being dry cleaned. The electricalconductivity of the emulsion is measured, for

instance, from time to time, and, if the electrical conductivity hasdropped to below the aforesaid value, an addiwithin thepredetermined'ranges. It will, of course, be

understood that after the fabrics are cleaned they are rinsed and driedand fluffed in accordance with standard practices in the art. I

It will be understood that the addition of oil-soluble dispersing agentor detergent to the organic solvent emulsions will occur.- far moreinfrequently than'the additions ofwater. In this connection, it will beappreciated that the solubility and stability of the oil-solubledispersing.

agent or detergent are such that the content thereof diminishesquiteslowly so that replenishing thereof is necessary at only relativelysporadic intervals. Hence,

when the electrical conductivity drops below about.

x 10'' mhosit will, in most cases, be necessary to add only water inorder to increase the electrical conductivity to a value above saidminimum figure. The content of oil soluble detergent in the dry cleaningemulsion can be determined from time to time by heretofore knownprocedures; It may be found, in certain instances, that when theelectrical conductivity drops below the aforesaid minimum value theremay be a deficiency of both detergent and water, and, in such cases,both detergent and water will be added to bring the amounts thereofwithin the desired or predetermined ranges as well as restoring theelectrical conductivity of the dry cleaning emulsion to a value notbelow said minimum figure. In the-usual case, however, as stated, wateradditions alone will be sufficient and the detergent content can bedetermined and maintained at desired proportions by procedures alreadyknown in the art.

- In the drawing, FIG. 1 illustrates a conventional type of dry cleaningsystem, except as pointed out below, showin g only the cleaning systemin schematic form and wherein the usual washer-filter-trap assembly isutilized, the rinse system being omitted since it is strictlyconventional and forms no part of our present invention although, ofcourse, it will be understood that the rinse system is utilized afterthe cleaning operation is completed. In FIG. 1, we show a simple unitwhich is utilized in the practice of the method of our invention.

FIG. 2 is a vertical section through the unit or device for determiningthe electrical conductivity of the dry cleaning emulsion.

FIG. 3 isja perspective view of the electrodes and supporting structure.

In FIG. 1, numeral 10' represents a conventional type of dry cleaningwasher or wheel connected through drain. 7 pipe 12 to the usual trap 14,pump 16 and filter 18. Connected into the line between the filter andwheel is the conductivity measuring device 20*, hereafter described indetail. As shown in FIG. 1, the device 20 is shown positioned in thedirect line between the filter and the return line to the washer inwhich case all of the filtered solvent passes through said device. Ifdesired, however, said device 20 can be positioned in a by-pass line sothat the filtered solvent will not pass through said device 20 exceptwhen an actual conductivity test is to be carried out.

The device 20 shown in FIGS. 2 and 3 provides a simple, effective meanswhich enables the dry cleaner readily to determine the electricalconductivity of his dry cleaning emulsions at any desired stage of hisoperation. Itcomprises a chamber 22 open at its top and provided with acover 24. Connected into the chamber 22 adjacent its top is an inletpipe 26 through which the dry cleaning emulsion is admitted to saidchamber 22. A flexible tube 28 made of a material, such as Neoprene,which is resistant to the action of organic solvents, leads toward thebottom of the chamber. The pipe 26 is provided with a valve 30-. A pipe32, serving as an outlet from the chamber 22 connects into the bottom ofthe chamber and joins, through a valve 34, a T 36. Extending from the Tis an outlet pipe 38 and overflow pipe 40, the open top of said overflowpipe being disposed just above the top of the electrodes.

The electrode assembly, denoted generally by numeral 42, is adapted tobe inserted and removed from the chamstance, Luci-te or polystyrene. Iheframe comprises side members 50, 52 which are provided with notches 54,

, 56in which opposite edges of the electrodes fit. The electrodes aresupported and fixed in vertical position by bottom and top members 58and 60* respectively. Reinforcing members 62, 64 are provided onopposite sides of the side members to impart strength and rigidity tothe frame. The transverse plates 66 land 68 serve to hold the electrodeassembly against tipping in the chamber 22. Vertical extension pieces70, 72 provide convenient grasping means for lifting the electrodeassembly out of the chamber, and they serve also to rest against theunderside of the cover to aid in holding the assembly in positionagainst movement. Electrodes 44 and 48 are electric-ally connected bywire 74 the ends of which may be soldered to said electrodes. Wirelead-s 76, 78, connected to electrodes 46 and 44 respectively, passthrough grommets 80, 82 in the cover 24, and are adapted to be connectedto anelectrical conductivity meter or measuring device (not shown) ofany suitable type.

' Although we have described a system wherein the required additions ofwater and detergent are made, for instance from time to time, by whatmay be called manual means, it will be seen that, if desired, equipmentcan be so arranged as to automatically measure the electricalconductivity of the dry cleaning emulsion and automatically control theaddition of water and/ or detergent in response to changes in electricalconductivity of the emulsion. This can readily be accomplished by theutilization of a measuring device wherein changes in the electricalconductivity of the emulsion during the subjection of the fabrics to theaction thereof during the dry cleaning operation are determined and,when the electrical conductivity falls below a predetermined value,valve means are opened to admit water and/or detergent, particularlywater, to

the-washer so that it is admixed with the dry cleaning organic solventemulsion to bring the detergent and/ or water content up to the desiredvalue. When such value is reached, in response to the increase in theelectrical conductivity resulting from such increased detergent and/orwater content, the valve means close and the supply of detergent and/ orwater is shut off.

The electrical conductivity values referred to above and in the claimsrepresent the reciprocal of resistance values in ohms obtained whenusing the herein described cell with brass plates measuring 6 x 5 /2inches spaced 0.160- inch apart and a standard ohm meter which employs apotential of 60 volts DC. It will be appreciated that, with differenttypes of cells and different cell constructions, different values may beobtained and such values may be reflected in terms of electricalconductance, electrical conductivity or electrical resistance. In anyevent, however, whatever the values may be and whatever the unit ofmeasurement may be,- to the extent that such values correspond to theherein disclosed and claimed electrical conductivity values obtained bymeasurement with a cell made as described above, they will, of course,fall within the scope of our present invention. We prefer to recite thevalues in terms of electrical conductivity for simplicity purposes sincethese values increase with addition of water j ble non-volatiledry-cleaning water-emulsifying detergent and (b) from about 0.2% toabout 0.4% of water so finely emulsified in said organic solvent as toform a substantially clear homogeneous emulsion, said emulsion having anelectrical conductivity between about 10 and about 120x 1O mhos,periodically measuring the electrical conductivity of said emulsion and,when said electrical conductivity drops below said lower aforesaidvalue, measuring the emulsifying detergent content of said emulsion,adjusting said emulsifying detergent content to bring it to within theaforesaid values, and, to the extent required to bring the electricalconductivity of said emulsion to within the aforesaid values, addingwater in the requisite amount.

2. In the dry cleaning of soiled fabrics, the steps which comprisecleaning successive batches of said fabrics with a continuouslycirculating filtered water-immiscible dry cleaning liquid organicsolvent containing (a) from about 1.5% to about 3% of an oil-soluble drycleaning wateremul'sifying detergent selected from the group consistingof sulfate and sulfonate detergents containing an alkyl group of atleast 8 carbon atoms, and (b) from about 0.2% to about 0.4% of water sofinely emulsified in said organic solvent as to form a substantiallyclear homogeneous emulsion, said emulsion having an electricalconductivity between about 50 and about l 10- rnhos, measuring theelectrical conductivity of said filtered emulsion and, when saidelectrical conductivity drops below said lower aforesaid value,measuring the detergent content of said filtered emulsion, adjustingsaid detergent content to restore it to Within the aforesaid values, andadding water in the requisite amounts to restorethe electricalconductivity of saidfiltered emulsion to within the aforesaid values.

References Cited in the file of this patent 1 UNITED STATES PATENTSKeeler Mar. 24, 1925 1,810,660 Kritchevsky et ai. June 16, 19311,935,264 Felix et al Nov. 14, 1933 2,024,981 Reddish Dec. 17, 19352,158,614 Reddish May 16, 1939 2,251,691 Richardson AugfS, 19412,271,635 Flett ,Feb. 3, 1942 2,475,023 Grimes July 5, 1949 2,552,088Davis May 8, 1951 2,614,026 Lascari Oct.16, 1952 2,621,673 Hodgens Dec.16, 1952 2,632,144 Borrell Mar. 17, 1953 2,715,833 Fulton et al Aug. 23,1955 FOREIGN PATENTS 392,931 Great Britain May .15, 1933 OTHERREFERENCES BulletinNo. T-292, Natl. Institute of Cleaning and Dyeing,Silver Spring, Maryland, Oct. 30, 1952 (4 pp.). (Copy available at Natl.Institute.) 7 ASTM Bulletin, No. 192, September 1953, pages (TP153) 63to (TPlSS) 68. (Copy available at ASTM Headquarters, Phila., Pa.)

2. IN THE DRY CLEANING OF SOLID FABRICS, THE STEPS WHICH COMPRISECLEANING SUCCESSIVE BATCHES OF SAID FABRICS WITH A CONTINUOUSLYCIRCULATING FILTERED WATER-IMMISCIBLE DRY CLEANING LIQUID ORGANICSOLVENT CONTAINING (A) FROM ABOUT 1.5% TO ABOUT 3% OF AN OIL-SOLUBLE DRYCLEANING WATEREMULSIFYING DETERGENT SELECTED FROM THE GROUP CONSISTINGOF SULFATE AND SULFONATE DETERGENTS CONTAINING AN ALKYL GROUP OF ATLEAST 8 CARBON ATOMS, AND (B) FROM ABOUT 0.2% TO ABOUT 0.4% OF WATER SOFINELY EMULSIFIED IN SAID ORGANIC SOLVENT AS TO FORM A SUBSTANTIALLYCLEAR HOMOGENEOUS EMULSION, AND EMULSION HAVING AN ELECTRICAL CON-